PROJECT TITLE :
Protograph-Based Raptor-Like LDPC Codes
This paper proposes protograph-based Raptor-like (PBRL) codes as a class of rate-compatible low-density parity-check codes for binary-input AWGN channels. Like the Raptor codes, exclusive-OR operations on precoded bits produce further parity bits providing in depth rate compatibility. Unlike Raptor codes, every additional parity bit within the protograph is explicitly designed to optimize the density evolution threshold. During the lifting method, approximate cycle extrinsic message degree (ACE) and circulant progressive edge growth (CPEG) constraints are used to avoid undesirable graphical structures. Some density-evolution performance is sacrificed to obtain lower error floors, significantly at short blocklengths. Simulation results are shown for info block sizes of $k=1032 hboxand sixteen,384$. For a target frame error rate of $10^-5$, at every rate, the $k=1032 hboxand sixteen,384$ code families perform at intervals one dB and 0.4 dB of each the Gallager bound and the normal approximation, respectively. The 16 384 code family outperforms the simplest known standardized code family, specifically, the AR4JA codes. The PBRL codes conjointly outperform DVB-S2 codes that have the advantages of longer blocklengths and outer BCH codes. Performance is kind of like RC code families designed by Nguyen et al. that do not constrain codes to have the PBRL structure and involve simulation within the optimization method at each rate.
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